For reasons such as religion, health, economy and ecological conservation, vegetarians or people who prefer vegetarian diets have become a big part of the population, creating great business opportunities in such food industry. In recent years, some unlawful businesses violate consumers' rights by adding animal-derived ingredients in food products for better tastes and lower costs. In order to protect consumers' rights and prevent unlawful profits by these businesses, the Bureau of Food and Drug Analysis in Taiwan started research and development for methods to detect animal-derived ingredient in food products in 2004. The Bureau of Food and Drug Analysis also conducts surveys and accepts complaints from the consumers. Detection methods can be used to determine the presence of animal-derived ingredients and differentiate the origins thereof (such as pork, beef, chicken, fish and others) in food products. The present invention has been submitted in a patent application in Taiwan (ROC (Taiwan) Patent Application Number 093128997) and is now being examined. Since there is no definite guideline for vegetarian diets, vegetarian food makers use different standards to manufacture their products. In fact, although most vegetarians can accept eggs and milk as part of their diets, it is still critical to differentiate between chickens and eggs in vegetarian food products for those who are strictly vegan. Such detection method can provide adequate consumer protection and also prevent unlawful business conducts in the industry of vegetarian food manufacture.
In general, morphology and specificity to components, such as proteins or DNAs, can be used to identify species. Different tissues or organs within a species are identified by the overall appearance of an organ, cells that form a tissue and specific components of a tissue. However, the appearance and cells of food ingredients (for example, meat, basically composed of muscle tissues) are usually destroyed after being processed, and are therefore unidentifiable in highly processed foods. Thus, detection of specific molecules in tissues should be the general method to identify the origins of ingredients in these food products. A specific DNA sequence can be detected to identify species. For example, in Meat Sci. 53:227-231, specific primer pairs were designated to identify the gene of chicken actin where PCR was performed. In addition, Poultry Science 83:2083-2085 disclosed several specific primer pairs designated for ATPase subunit 8 genes. Although patent application Ser. No. 093128997 presented a detection method for identifying animal-derived ingredients in food products using specific primer pair and probe designated from highly conserved DNA sequence of animal in real time PCR, this invention merely identified the origins of ingredients in food. Because DNAs in different organs and tissues are identical for a single species, if one wishes to differentiate the ingredients from different tissues of the same species, the above detection method, which uses the DNA sequence specific to species, is not able to do that.
Although DNAs of different tissue cells are identical within a species, they have “tissue specific expression” and the proteins of such “tissue specific expression” can be targeted to distinguish the tissue cells from different origins within a species. This method has been disclosed in Shokuhin Eiseigaku Zasshi (J. Food Hyg. Soc. Japan) 47(4): 189-195, Shokuhin Eiseigaku Zasshi 43(4): J275-J279 and Allergy 54(5): 464-472, which uses antigens or allergens, such as ovalbumin in eggs, to detect egg ingredient in food products. However, according to the research report in Shokuhin Eiseigaku Zasshi (J. Food Hyg. Soc. Japan) 47(4): 189-195, the detection method by using tissue specific expression may produce false positive result because of cross-reaction, so it cannot accurately differentiate between chicken- and egg-derived ingredients in food.
For the above reasons, no prior art can be used to differentiate (or accurately differentiate) between chicken- and egg-derived ingredients in food. Hence, there is still a need for a precise detection method.